diff --git a/study_guides/react_redux/pokedex_debugger/Gemfile b/study_guides/react_redux/pokedex_debugger/Gemfile
index 123b23786..dc4f240ee 100644
--- a/study_guides/react_redux/pokedex_debugger/Gemfile
+++ b/study_guides/react_redux/pokedex_debugger/Gemfile
@@ -11,7 +11,7 @@ gem 'rails', '~> 5.1.2'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 1.0.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.12'
+gem 'puma', '~> 4.3'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets
diff --git a/study_guides/react_redux/pokedex_debugger/Gemfile.lock b/study_guides/react_redux/pokedex_debugger/Gemfile.lock
index 74288a1c5..870a1d1d4 100644
--- a/study_guides/react_redux/pokedex_debugger/Gemfile.lock
+++ b/study_guides/react_redux/pokedex_debugger/Gemfile.lock
@@ -94,7 +94,8 @@ GEM
       mini_portile2 (~> 2.4.0)
     pg (1.1.4)
     public_suffix (4.0.1)
-    puma (3.12.6)
+    puma (4.3.11)
+      nio4r (~> 2.0)
     rack (2.2.3)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -182,7 +183,7 @@ DEPENDENCIES
   jquery-rails
   listen (>= 3.0.5, < 3.2)
   pg (>= 1.0.0)
-  puma (~> 3.12)
+  puma (~> 4.3)
   rails (~> 5.1.2)
   sass-rails (~> 5.0)
   selenium-webdriver